The enzyme DAPA aminotransferase has been purified over 1000-fold, and the properties of the enzyme studied. The kinetics show the ping- pong mechanism observed in all aminotransferase reactions. We have also been able to show an active transport process in E. coli K-12, Y10-1, which shows primarily free biotin while a deletion and a point mutant show both free and bound biotin. A number of alpha-dehydrobiotin resistant mutants have been isolated and divided into 5 groups, R-,Oc, permeability for biotin, generalized permeability, and unknown.